Head Removal. To proceed or not to proceed

[Jonny B]

Very nice indeed. What is the red around the four cam bearings?

[Tyler S]

Jonny, Assembly Lube. It goes on all contact surfaces. Unlike oil it stays put until you run the engine. Don't want a dry start.
Tyler

[Benz Dr.]

I spin the engine over with the starter, spark plugs removed, until I get full oil pressure. Almost no load on any moving parts. I tried using an electric drill once and it almost broke my arm when I hit oil pressure. I figure the starter is a bit safer.

[Tyler S]

Dan, Going to do that as well. With the valve cover off until I get flow to the cam oiler tube. Going to break in the cam @2500 RPM once it starts so I want that little bit extra insurance.

[rgafitanu@gmail.com]

Tyler,
I have a question, maybe I am getting this wrong (BTW the post is great I wish you to enjoy it once finished). You (they) took 0.003 from top and 0.003 from the bottom of your head. While skimming from the top drops the position of the camshaft wrt everything else (since the bearings are on the skimmed surface), skimming from the bottom reduces (only) the volume of the combustion chamber. In my mind, in order to correct the camshaft positioning I would shim it only for the top skim 0.003. If you are shimming the camshaft for the total 0.006 aren't you overcompensating, possibly affecting the valve kinematics? Or maybe I am missing something.

Radu

[Tyler S]

Radu, Yes and No. Keep in mind my valve seats were ground so the valve stem height is actually a slight bit higher than before.
You want to shim the cam towers to bring the cam back to the height before the repair (measured from the block) so the total shim thickness would be as close to what was milled (top and bottom) as possible. This allows the timing chain to ride in its original path and keep the valves in time. If you were to leave out the shims or cut the measurment in half, The cam timing would be retarded as well as the possibility of the tensioner maxing out. As far as valve/rocker geometry, this will be made up with the correct thickness thrust washer pieces that sit on top of the valve stems. This determination is made last after the cam, rockers, and ball studs are installed. Hope that makes sense.
Tyler

[Pinder]

I used the same assembly lube. It worked out great. I also cranked the engine until there was oil visible at top. Spark plugs removed when that was done. Looks like your making great progress.

[Tyler S]

Pinder, Getting there. Im taking my time and detailing components as they go back on the engine. Cleanup, paint, and aluminum cleaning takes way longer than the actual repair. 

[Pinder]

Yes takes time but worth the effort. especially if you cleanup the manifolds and valve cover plus the intake throttle body. I also cleaned up my wiring harness. I found lacquer thinner works pretty good to get the gunk off on the wire harness.

[erickmarciano]

just removed the head and a few exh valves have a whitish crust on them
What can this be?
Thanks

[Tyler S]

Erick, Mine looked almost identical. Its ash. Most likely from burning oil.
My valve guides and seals were the culpret.
Check out the photos of them on page 1 of this post

[erickmarciano]

Got some ban news
Car ran amazing till I got bored and decided to remove the head for a little oil burning
The head has never been cut but one of the combustion chambers has been re welded . Does this look critical?
Would you reuse it or use an alternate head that measures 84.6?
Thanks

[Tyler S]

Have the machine shop pressure test the head and then make a determination. If it was welded properly I dont think its anything to worry about. It must have burned a seat sometime in its life if it has never been decked.

[erickmarciano]

Great.  It has never been welded showed a local Mercedes wiz
He said the same thing burnt seat
What would cause that whole area to be eaten up?
Thanks

[Benz Dr.]

We weld up heads quite often. The water ports in the head will often corrode away and will need to be replaced. Sometimes the head will have corrosion around these water inserts so that would need to be welded. If the head is straight a very minimal cut would be needed to clean everything up.

 I'm thinking a coolant leak in the head gasket caused it to corrode the chamber and maybe enough for the valve seat to come loose. We have had to weld the seat recess back in, machine a new area to accept the seat, and then install a new seat. After the seat is installed it would need to be cut to fit the valve. Only someone skilled with the proper machines can do this sort of work. Maybe not rocket science but not easy to do either.   

[erickmarciano]

Thanks for the reply
The piston is pitted for that cylinder
Car ran great. Compression was 150 except the one with a lose guide at 130
Should I leave it like that?
Thanks

[ja17]

Erick,

The stock thickness is 85mm. 

[Tyler S]

That was either caused by a lean burn or detonation. Probably a result of the burned exhaust seat. Double check your injectors after the repair. That single cylinder could have been running lean do to a bad injector.
I have seen engines put back together and ran with that kind of pitting. Its a gamble. Personally, I wouldn't run it like that. If it goes and you ruin the block then you will be out of pocket way more then you will be fixing it now.

[Benz Dr.]

That's a 280 block - are you putting it in your car? That piston isn't in great shape.

[Pinder]

If the engine is already out of the car it wont take too much more work to put new pistons in. second repair pistons are relatively cheap on the internet for around $650.

[Tyler S]

Lots of progress. Installed the new ball studs, rocker arms, rocker clips, and 3.5 mm thrust spacer shims. The valve geometry is almost perfect. The ball studs are exactly at the middle of their travel and the rockers are uniform and parallel. I can't believe how much tighter everything is with new parts! The old spring clips could almost be removed with your thumb nail.
What a joy it was setting up the valve clearances for the first time after assembly. My knees are killing me. 
So as it stands I am now back to where I started with the original project of replacing the manifold gasket.
Still lots to do but I see an end soon. Replaced the starter with the higher cranking amp one since it was easily accessable with the manifolds removed. Also replaced the battery cables.
New water pump, oil pan, oil pump pickup screen and gasket, side cover plate, every single seal and gasket with the exception of the rear main.
Cleaning up and painting all the ancillaries and brackets before they go back on the car.
A few days before contact I hope. The pile of "Star" wrappers is getting excessive
Happy Saint Patty's Day! 
Tyler

[Pinder]

Looks Fantastic Tyler! I admire your attention to detail.

[ja17]

Eric,

Water in the combustion chamber can also cause the pitting in the piston top. I have never seen the pitting cause any problems.

[Benz Dr.]

It will eventually fill up with carbon and look like the rest on the piston tops.

 I would polish off any sharp edges to avoid any places where you could get a glowing piece of carbon sticking out from the top of the piston. Not much of a problem with our cars but it is a big problem in 190SL's that tend to run on after shut down from this exact situation.

[erickmarciano]

Thanks for the encouragement